Perylene and naphthalene bisimides are two of the most widely studied π-conjugated molecules due to their tendency to form n-type (acceptor) semiconducting materials. Similarly, oligophenylene vinylene (OPV) is a well-studied p type (donor) semiconducting material. However, discrete one-dimensional nanoobjects based on these materials are still very rare despite their potential in nanotechnologies. Nanostructuring plays an important role in the device applications such as optoelectronics and photovoltaics; since the charge carrier mobility varies with various packing arrangements. Ideally, the donor and acceptor material should form a bicontinuous and interpenetrating network with an interfacial distance smaller than the exciton diffusion length (10-20 nm). Block copolymers have the potential to microphase separate and form well-defined arrays which are tens of nanometers in size.
J. Ruokolainen et. al in Macromolecules 1999, 32, 1152-1158 discloses a preparation of the polymeric materials i.e. supramolecular comb-coil diblock copolymers from amphiphilic compound i.e. 3-n-pentadecylphenol and polystyrene-block-poly(4-vinylpyridine) by the hydrogen bonding interactions between the pyridine group of poly(4-vinylpyridine) and hydroxyl group of 3-n-pentadecylphenol unit. Further, the polymeric materials are characterized by two length scales, “block copolymer length scale: 10-100 nm” and a shorter “nanoscale: ˜3 nm”.
Stefan M. Lindner et. al in Macromolecules 2004, 37, 8832-8835 discloses the synthesis of donor-acceptor block copolymer i.e. poly(vinyltriphenylamine)-b-poly(perylenebisimide acrylate) [PvTPA-b-PPerAcr] by subsequent polymerization of perylenebisimide acrylate and vinyltriphenylamine monomers in presence of o-dichlorobenzene at a temperature of 125° C. via nitroxide mediated radical polymerization.
The thin film field-effect transistors containing blend of poly-3-hexyl-thiophene (P3HT) and perylene diimide (PDI) is reported by Sreenivasa Reddy et. al in J. Mater. Chem. C, 2013.
Further, Qingling Zhang et. al in Macromolecules 2009, 42 (4), 1079-1082 discloses the preparation of donor-accepted diblock copolymer comprising poly(3-hexylthiophene) (rrP3HT) and poly(perylene diimide acrylate) (PPDA) useful for fabrication of solar cell. Further, the vinyl terminated rrP3HT is synthesized using Grignard metathesis polymerization and converted to polythiophene macroinitiator, which is then used in controlled free radical polymerization of a perylene diimide containing acrylate to give said donor-acceptor copolymer. The preparation of donor accepted diblock copolymer employs costly Grignard reagent and metal catalyst in presence of inert solvent.
Rancatore et. al in ACS, 2010, Vol. 4, No. 5, 2721-2729 discloses the fabrication of organic semiconductor-based devices using solution processing; wherein quarter thiophene organic semiconductor i.e. 5′″-(3,7-Dimethyloctyl)-5-(3-(3-hydroxyphenyl)propyl)-[2,2′;5′,2″;5″,2′″] quarter thiophene compound [4T] is attached to the side chains of block copolymer of poly(styrene)-block-poly(4-vinylpyridine) [PS-b-P4VP] by noncovalent hydrogen bonds to obtain supramolecular assemblies that act as p-type semiconductors in field-effect transistors.
From the aforementioned examples, the blending of low molecular weight perylene imides with thiophene polymers to prepare smooth films of field-effect transistors involves inherent problem of macrophase separation. Additionally, the preparation of supramolecular complexes and semiconductors involves cumbersome, hazardous chemicals and reagents, and lengthy process steps hence commercially not feasible.
Further, the use of perylene and naphthalene bisimides in applications such as organic field effect transistors and solar cells requires considerable effort to overcome their low intrinsic stability. Thus, the perylene bisimides when covalently tethered to a polymer back bone either in main chain or as side groups of block polymers gains in terms of solution processability and microphase separability, but looses in terms of intrinsic crystallinity of the small molecules.
In view of foregoing, there is need in the art for the facile organization of both n-type (i.e. acceptor materials) and p-type (i.e. donor materials) organic semiconductor materials in the form of an interpenetrating structure in the nano domain, thereby making efficient charge separation in device application of organic field effect transistors (OFET) and solar cells. Thus, the present invention overcomes the technical constraints by combining solution processability with crystallinity in perylene bisimide derivatives using supramolecular complexation of perylene bisimide derivatives to poly(4-vinyl pyridine) polymer via hydrogen bonding.